Lewis said his wife died in a honeymoon accident. Then a more gruesome theory emerged.

From the moment US coast guards found Lewis Bennett floating alone in a life raft near the Bahamas, the former Gold Coast businessman has maintained his wife’s death was a tragic accident.

But on Monday, that could change.

According to Florida newspaper The Ledger, the dual British/Australian citizen is expected to make a plea deal with US prosecutors, accepting a reduced charge of involuntary manslaughter over the death of Isabella Hellmann, who vanished when their luxury 37-foot catamaran sunk in May 2017.

The Columbian-born woman’s body was never found.

The mysterious collision and the stolen coins.

Bennett, 41, and Hellmann had been married for three months and were returning home to Florida from their belated Carribbean honeymoon when Bennett made an SOS call to say his boat was sinking.

The former Gold Coast businessman told authorities that he was sleeping below deck when he was jolted awake by what felt like a collision with an unknown object. Bennett said he scrambled topside and jumped on a lifeboat, but his wife – who had agreed to take watch and was wearing a life jacket – was nowhere to be seen.

In the lifeboat with Bennett was a bag filled with roughly US$40,000 (AUD$55,500) worth of gold and silver coins; coins that prosecutors later proved he had stolen from his boss while working as a crewman on a yacht in 2016.

Bennett was convicted of the theft and is currently serving seven months in a Miami prison.

But in February, prosecutors added a more serious crime to Bennett’s rap sheet, when they charged him second-degree murder.

Marital strife.

According to the Sun-Sentinel, investigators believed that rather than suffering a collision, the vessel had been "intentionally scuttled". They discovered that the catamaran had sustained seemingly deliberate damage from the inside, and that escape hatches below the waterline had been opened, causing the cabin to flood.

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Prosecutors alleged that Bennett killed his wife in order to free himself of "marital strife". They alleged that the pair had been arguing about finances and where to raise their young daughter, who now lives with Bennett's relatives in the UK.

Court documents revealed Bennett and Hellmann owed property taxes and also faced having their condo’s electricity cut off, and also catalogued tense text messages between the pair.

"This morning I was afraid to get home with the coffee but I walked in and I was right,” one text message from Hellmann read, according to The Times. “I found an angry person, this is very sad.”

“Sometimes I can be a pain in the a** and more but you need to change your attitude… you make me crazy shouting, yelling, swearing… YOU ARE PUSHING ME AWAY,” read another.

According to The Ledger, shortly after the honeymoon tragedy, Bennett filed a motion with the Florida courts asking that his wife be declared dead; a move that would have given him possession of their condominium and other items that belonged to her. A judge rejected the motion.

The new deal.

If convicted under the murder charge, Bennett was facing 17 years in prison. If he accepts the manslaughter plea deal, he faces a maximum of eight years plus likely deportation.